There is now excellent evidence that supermassive black holes
reside at the centers of most or all massive galaxies. There are
two majour, complementary ways of finding these black holes.
One measures the motions of a large number of stars at large
distances from the the black hole, while the other is based on the
disruptive influence of black hole tidal forces on individual stars
in the immediate vicinity of the black hole. The first method let to
the important discovery of scaling relations between the properties
of host galaxies and the masses of the black holes that reside at
their cores. Narrow-line Seyfert 1 galaxies are a subclass of Active
Galaxies which harbor low-mass black holes accreting at a very
high rate, therefore growing rapidly. As such, they are important
test-beds as to how black holes and their host galaxies co-evolve,
and how the scaling relations hold under these conditions. I
present our recent results on how these galaxies follow the M-sigma
relation. A subclass of them turns out to be characterized by very
strong outflows which may be driven by the strong radiation
pressure from their accretion disk. The second part of my talk will
address new results regarding the second method of black hole
detection; the tidal disruption of stars by supermassive black holes,
and the recent discovery of a light-echo from gas in the host galaxy,
excited by the bright flare of radiation that is produced when the
stellar tidal debris is accreted by the massive black hole.